The different parts and their functions
Before reaching the wheels and brakes proper and from the moment when the pilot presses the pedals to give the braking order, it travels through a complete circuit making up the braking control system, and which effectively controls braking. This system is essentially composed of three parts, each with a specific function:
Regulation, which has two principle functions:
- the transmission of the order (given by the pilot) and its transformation into braking orders.
On most aircraft this function is assured through electric signals that go through a braking computer, called the BSCU (Braking and Steering Control Unit). This why we talk about "Brake by Wire".
With the A380 and the arrival of Integrated Modular Avionics (IMA), the specific braking computer is partly replaced by electronic modules that are common to several functions. The software is specific to the braking function.
To find out more: the A380
- theenergy activation, which allows braking.
This energy is hydraulic, generated by the aircraft engines. It is activated by means of a solenoid valve, which sends oil under pressure into the braking circuit.
According to the "decentralised energy" concept that appeared with the A380, this system may be replaced by local micropumps, activated by small electric motors, all of which make up the EHA (Electro Hydrostatic Actuators) which positioned close to the wheels locally supply the hydraulic power necessary for the brakes.
To find out more: decentralised hydraulics
Energy distributors
In the traditional hydraulic system they are servo-valves, letting the oil sent by the solenoid valve pass through with more or less pressure to hydraulic pistons in the brake depending on the information transmitted by the BSCU, itself resulting from the force with which the pilot presses the pedal. With the EHAs, they send the oil directly to the pistons
Later, on the "electric aircraft", the plan is to replace these hydraulic actuators with electric motors, the EMA (Electro Mechanical Actuators), in place of the present pistons. With this type of brake the hydraulic part will disappear completely, making way for "all electric".
To find out more: electric braking
An alternate circuit, able to take over from the main circuit in the event of its failing.
Traditionally hydro-mechanical, this may now be modelled on the normal circuit, electrically controlled, benefiting from a second computer and able to activate the hydraulic actuators. This is why this time we talk about "Full Brake by Wire".
